Electromagnetic projectile launcher with an augmented breech

This invention relates to electromagnetic projectile launchers and more particularly to such launchers with a rail geometry which provides an augmented electromagnetic field in the breech area.

Electromagnetic projectile launchers are known which comprise a pair of conductive rails, a sliding conductive armature between the rails, and means for commutating a large direct current into the rails and through the armature. Current flow places an electromagnetic force on the armature which propels it along the conductive rails. An early launcher employing this concept is disclosed in U.S. Pat. No. 1,370,200, dated Mar. 1, 1921.

Prior to acceleration, conductive armatures are either stationary in the rail breech area or are inserted into the breech area at a relatively slow velocity. In order to develop an electromagnetic launcher capable of rapid firing, a technique for initiating projectile motion without damaging the projectile armature or the breech rail section is essential. The early stages of acceleration are most critical in this regard since high current density current transfer is most difficult to achieve without damage at zero or very low velocities. Copending application Ser. No. 137,059, filed Apr. 3, 1980 by Kemeny and Litz, now U.S. Pat. No. 4,347,463 entitled "Electromagnetic Projectile Launcher With Self-Augmented Rails", and assigned to the present assignee, discloses a launcher which employs additional conductors parallel to the rails to increase force on an armature for a given rail current. These additional conductors can run the full length of the rails and add significant resistance and inductance to the rail system. The present invention seeks to increase armature acceleration in the breech area for a given rail current to minimize rail and armature damage. This is accomplished with relatively short breech augmenting rail configurations, thereby minimizing resistive and inductive effects of the augmentation. Limiting augmentation to the breech area also minimizes launcher weight at the muzzle end thereby maintaining launcher maneuverability. Both parallel and nonparallel rail geometries are used to achieve breech augmentation. Since augmentation occurs during current commutation into the breech, peak acceleration of the armature and projectile need not be increased.

This invention comprises: a pair of conductors in the form of rails; a movable conductive armature between these rails; a source of high current; a switch for commutating this current to the rails and armature; and means for increasing the magnetic field in the breech area comprising, a breech augmenting conductor rail assembly which increases the electromagnetic force on a projectile in the breech area for a given current. One embodiment of this breech augmenting rail assembly comprises additional rails which are parallel to the first pair of rails and located near the breech section. These additional rails are located adjacent the pair of conductive rails and carry current in a direction which augments the electromagnetic field in the breech area.

A second embodiment of the breech augmenting rail assembly provides for augmentation of the electromagnetic field in the breech area through the use of a nonparallel rail geometry where the pair of conductive rails are bent at an angle near the breech area. This produces a repulsive magnetic field between a section of rail and the movable armature which serves to increase initial armature acceleration.

FIG. 1 shows an embodiment of an electromagnetic launcher with breech augmenting rails in accordance with the present invention;

FIG. 2 shows a cross-sectional view of the breech area of an electromagnetic launcher with a plurality of breech augmenting rails in accordance with an embodiment of the present invention;

FIG. 3 shows a typical current-time relationship for an electromagnetic launcher and illustrates the effect of breech augmentation on armature acceleration; and

FIG. 4 shows the breech area of an electromagnetic launcher utilizing a nonparallel augmentation system in accordance with an embodiment of the present invention.

FIG. 1 shows an embodiment of an electromagnetic projectile launching system in accordance with the present invention. The series circuit comprising generator 10, induction coil 12, and switch 14 is connected between augmenting rail 16 and barrel rail 28. Circuit breaker 15 is connected in parallel with this series circuit and provides a means for rapidly commutating current into augmenting rail 16 and barrel rail 28. Augmenting rails 16 and 20 are disposed generally parallel to the breech ends of barrel rails 24 and 28 respectively. Insulator 30 separates augmenting rail 16 and barrel rail 24. Insulator 32 separates augmenting rail 20 and barrel rail 28. Shunt 18 connects the ends of augmenting rails 16 and 20 which are opposite the breech ends. Shunt 22 is disposed on the side of barrel rails 24 and 28, opposite that of shunt 18 and connects the breech ends of augmenting rail 20 and barrel rail 24.

When switch 14 is closed, generator 10 charges induction coil 12 to maximum current. At that time, circuit breaker 15 is opened, commutating current to the launcher rails. The arrows in FIG. 1 illustrate that the current I flows through augmenting rail 16, shunt 18, augmenting rail 20, and shunt 22 into barrel rail 24. Then it flows through movable armature 26 and barrel rail 28, back to generator 10. This creates electromagnetic forces which propel armature 26 along barrel rails 24 and 28.

Since current flow in each augmenting rail 16 and 20 and the closest barrel rail 24 and 28, respectively, is in the same direction, the resulting electromagnetic forces in the breech area are greater than those found in a launcher which does not utilize breech augmenting rails. Therefore, armature 26 is subjected to larger forces and its acceleration is increased. This minimizes damage to the breech area of the barrel rails 24 and 28 by shortening the time required to achieve a desired armature speed. Alternatively, a smaller current could be used to attain the acceleration found in launchers which do not utilize augmenting rails.

Shunts 18 and 22 are arranged on opposite sides of barrel rails 24 and 28 in order to balance electrical forces in the breech area. The augmenting rail lengths can be varied to achieve a desired level of acceleration. It should be apparent to those skilled in the art that the breech augmentation system shown in FIG. 1 can also be used on launchers which employ multiple barrel rails.

Additional breech augmenting rails could be added to the launching system of FIG. 1 without departing from the scope of this invention. FIG. 2 shows a cross section of the breech area of a launcher with ten augmenting rails. The current through augmenting rails 20, 38, 40, 42 and 44 would travel in the same direction at the current in barrel rail 28. Similarly, the current through augmenting rails 16, 34, 36, 46 and 48 would travel in the same direction as the current in barrel rail 24. Shunt conductors between the rails would be arranged such that an equal number pass above and below the barrel rails.

Augmenting rail lengths would typically range from ten to twenty centimeters. Since this is small in comparison to typical barrel rail lengths, the series resistance of the augmenting rails will not adversely affect system performance.

FIG. 3 shows a typical current-time relationship for an electromagnetic launcher starting at the point where current commutation into the breech begins. The commutation time, shown here as 0.5 msec, can vary from 0.25 to 1.0 msec based on present switch designs. Acceleration time can vary from 1.5 to 3.0 msec for high velocity systems and up to 1.0 sec for low speed systems. The acceleration, a, is proportional to the current squared, I 2 . In FIG. 3, I represents current and a 1 represents the acceleration as a function of time for a barrel configuration consisting of a pair of barrel rails without augmenting rails. By adding one set of augmenting rails as illustrated in FIG. 1, the acceleration can be increased to that shown by a 2 in FIG. 3. The length of the augmenting rails is adjusted such that the maximum acceleration is not exceeded, thereby avoiding stress problems in the launch package.

The use of breech augmentation rails thus increases armature velocity at a faster rate and also initiates sliding current transfer at a lower current, both of which will reduce the likelihood of armature or rail damage. Depending upon the increased force desired in the breech area, any combination of augmentation rails can be added as illustrated by FIG. 2.

An alternative embodiment of the breech of an augmented breech launcher is shown in FIG. 4. A nonparallel rail geometry is shown in which additional force is obtained from rail section 50 since its magnetic field will increase the total magnetic field behind armature 26. This force will decrease rapidly as the armature moves out of the breech area. Barrel rails 24 and 28 are bent to form a right angle at the launcher breech, and positioned equidistant from each other. This provides for a generally parallel arrangement of armature 26 and rail section 50.

While specific embodiments of the invention have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the invention which is to be given the full breadth of the appended claims.